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Old 09-15-16, 08:48 AM   #4
Aktungbby
Gefallen Engel U-666
 
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The following tables were started from a description in the book Type VII U-boats, by Robert C. Stern, ISBN 1 86019 8554, 1998 edition. It is hoped to add to this description. 1. An electric bell gives the alarm. 2. The bridge watch prepares the bridge (close voice tube, demount portable machine guns, remove water-tight binoculars from UZO, remove radar detector aerial if necessary, etc.). 3. Simultaneously, vent valves for ballast tanks 5, 2/4, Quick diving tank (if empty) and 3 are opened in that order flooding from bow to stern to overcome the natural stern heaviness of the boat. If fuel is in ballast tanks 2 and 4, the main vent valve is opened with the inner vent valve remaining closed to equalize pressure in the ducts. 4. Simultaneously, the Petty Officer of the Watch goes below to his action station at the forward hydroplanes; the port quarter look-out follows to his action station in the conning tower with the Commanding Officer. The starboard quarter look-out goes below to the after hydroplanes. The Officer of the Watch is the last to go below. It is his duty to close the conning tower hatch. He then goes to his action station in the Control Room. 5. Simultaneously, close Supply and Exhaust air ventilation valves and any other openings in the pressure hull. 6. Planesmen position fore plane down and stern plane up. If it is a crash dive personnel not on watch might be ordered to move to the forward torpedo room to help get the bow under water. Initial angle of dive 4-7° to avoid propellers "racing". 7. Simultaneously, engine room personnel shut down and unclutch Diesel engines and shut the external air intake and exhaust valves. 8. Simultaneously, electric motor room personnel start electric motors 9. When the desired down angle is achieved (normally 12-15° but can go as high as 30 ° in a crash dive - at more than 40° acid may leak from battery cells) vent valve for ballast tank 1 is opened. 10. Simultaneously, the planes are brought to neutral position. Shut off Papenberg depth gauge at 18 meters and precision depth gauge passing 20 meters. 11. Quick diving tank is blown just short of empty to avoid releasing bubbles. This should result in the boat being at slightly positive buoyancy because the Regulating/Compensating tank is adjusted and maintained to achieve that. 12. Once tanks are flooded, the valves are shut 13. When desired depth is approached forward dive planes were moved up and stern down to level the boat at desired depth. 14. Boat is maintained at depth dynamically by use of the dive planes. 15. Because teh pressure hull is compressed with increasing depth the boat would grow heavier and the ballast pump or compressed air would be used to keep the boat at slightly positive buoyancy the opposite would occur if the boat moved to a shallower depth and water would be taken in.
http://www.uboatarchive.net/KTB/KTBNotesDiving.htm
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